In recent years, a number of automated systems have been developed for carrying out quantitative chemical analyses of sample fluids. Such automated systems have proven particularly advantangeous for use in clinical laboratories, especially in the analysis of blood.
For example, U.S. Pat. No. 4,296,069 discloses an apparatus which performs chemical analysis of a sample fluid deposited on an analysis test slide. A slide transfer mechanism selectively transfers an analysis test slide between an incubator and a read station. Following analysis at the read station, the test slide is either returned by the slide transfer mechanism to the incubator or is discarded by the transfer mechanism.
Different types of analysis test slides, as for example colorimetric and potentiometric slides, may be used in chemical analyzers. Although such test slides may be dimensionally similar, they have geographically different fluid deposit zones defined thereby. That is, the sample fluid applied to the test slides for analysis is applied in different locations or zones on each type of slide.
Some chemical analyzers have a sample fluid deposit device including a dual tip pipette which allows selective fluid application to both types of test slides. Because of the geographically different deposit zones on the test slides, however, the two different types of slides must be positioned differently beneath the pipettes. This is a timely and therefore, expensive procedure.
U.S. Pat. No. 4,041,995 discloses a chemical analyzer which carries test slides on a vertically movable support. This device, however, does not apply sample fluids to both colorimetric and potentiometric test slides in the same test slide holder. Moreover, there is no provision for moving the test slides in other than a vertical plane.
Presently available chemical analyzers have applied fluid to the two types of test slides in two different stations and the positioning problem has not been addressed. Moreover, certain sample fluids do not readily wick onto a test slide. Therefore, such sample fluids are not easily separated from the pipette tip and applied to the test slide by the action of the pipette alone. Other sample fluids do not readily bridge the gap between the pipette tip and the test slide and tend to wet the side of the pipette tip, hereinafter called "perfusion". Both problems are further aggravated by microgravity environments.
Analyzers used in space stations to monitor the health of astronauts have an additional constraint--the parts and test elements thereof must be kept confined lest they become floating objects that can be dangerous.